Aqueous coating material composition and method for forming multilayer coating film

Abstract

The purpose of the present disclosure is to provide an aqueous coating material composition that has exceptional storage stability and can exhibit high coating film performance and glass adhesiveness even when cured at a comparatively low temperature. An aqueous coating material composition containing (A) a hydroxyl group- and carboxyl group-containing resin, (B) an aqueous dispersion of a blocked polyisocyanate compound; and (C) a polycarbodiimide compound, wherein the (B) aqueous dispersion of a blocked polyisocyanate compound contains a blocked polyisocyanate compound (b1) and at least one anionic surfactant (b2) selected from sulphonates and sulfates.

1 . An aqueous coating composition comprising:
 a hydroxyl group- and carboxyl group-containing resin (A);   a blocked polyisocyanate compound aqueous dispersion (B); and   a polycarbodiimide compound (C),   wherein the blocked polyisocyanate compound aqueous dispersion (B) comprises a blocked polyisocyanate compound (b1) and at least one anionic surfactant (b2) selected from sulfonic acid salts and sulfuric ester salts.   
     
     
         2 . The aqueous coating composition according to  claim 1 , wherein at least a portion of a blocking agent of the blocked polyisocyanate compound (b1) is an active methylene-based blocking agent. 
     
     
         3 . The aqueous coating composition according to  claim 1 , wherein a content of the anionic surfactant (b2) is in a range from 0.1 to 10 parts by mass based on 100 parts by mass of a solid content of the blocked polyisocyanate compound (b1). 
     
     
         4 . The aqueous coating composition according to  claim 1 , further comprising a melamine resin (D). 
     
     
         5 . A method of forming a multilayer coating film comprising, in sequence:
 (1) applying the aqueous coating composition according to  claim 1  onto an object to be coated to form an intermediate coating film;   (2) applying an aqueous basecoat coating composition onto the intermediate coating film formed in (1) to form a basecoat coating film;   (3) applying a clear coating composition onto the basecoat coating film formed in (2) to form a clear coating film; and   (4) heating and curing all at once the intermediate coating film, the basecoat coating film, and the clear coating film formed in (1) to (3).